Method and apparatus for testing shafts

ABSTRACT

Methods and apparatus are provided for testing shafts, such as golf club shafts. In one embodiment, the invention can be characterized as a shaft tester comprising: a frame; a first shaft support supporting a first portion of a shaft at a first fixed position; a second shaft support supporting a second portion of the shaft at a second fixed position; and a third shaft support supporting a third portion of the shaft at a third fixed position. An actuator couples to the third shaft support to displace the third portion relative to the first and second portions to deflect the shaft. A sensor couples to one of the first, second and third supports outputting a signal corresponding to a force exerted by the shaft due. A controller controls displacement of the shaft. In some embodiments, the shaft is rotated while being deflected.

This application is a continuation of U.S. application Ser. No.12/110,243, filed Apr. 25, 2008, which claims the benefit of U.S.Provisional Application No. 60/914,015, filed Apr. 25, 2007, both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the testing shafts, and morespecifically to testing of golf club shafts.

2. Discussion of the Related Art

Currently there are a variety of devices to test the durability of ashaft. Different tests have been designed and developed to filter outshafts that don't have acceptable structural strength. For example, inthe golf industry, a commonly used shaft destruction test is the aircannon test, whereby a ball is shot at a golf head at a specified speeduntil an acceptable impact quantity is reached or there is acatastrophic break (the head is bonded to the shaft as would be in thefield). This test requires multiple iterations (often times up to 3000hits and beyond). Additionally, air cannon tests are time consuming,noisy, require human supervision and are potentially dangerous(essentially since a projectile is launched at high speed toward theclub head).

The above-described methods test the structural integrity of a compositegolf shaft. At least one problem with these methods and other compositegolf shaft testing methods is that all of these tests focus on onesingular location or point on the shaft and not at different points ofthe or the entire circumference. This type of testing can lead to a“false positive” destructive test result. One reason for a “falsepositive” result is because of composite ply drop offs. Variations inshaft wall thickness caused by ply drop-offs or poor designs can lead tostrength variations in the shaft about its circumference.

SUMMARY OF THE INVENTION

Several embodiments of the invention provide methods and apparatus fortesting shafts, such as golf club shafts. In one embodiment, theinvention can be characterized as a shaft tester comprising: a frame; afirst shaft support coupled to the frame, the first shaft supportadapted to support a first portion of a shaft at a first fixed position;a second shaft support coupled to the frame, the second shaft supportadapted to support a second portion of the shaft at a second fixedposition; and a third shaft support coupled to the frame, the thirdshaft support adapted to support a third portion of the shaft at a thirdfixed position. The shaft tester also comprises an actuator coupled tothe third shaft support and adapted to displace the third portionrelative to the first portion and the second portion to cause adeflection in the shaft; a sensor coupled to one of the first support,the second support and the third support and adapted to output a signalcorresponding to a load force exerted by the shaft due to thedeflection; and a controller coupled to the actuator and adapted tocontrol displacement of the shaft.

In another embodiment, the invention can be characterized as a shafttester comprising: a frame; a first shaft support coupled to the frame,the first shaft support adapted to support a first portion of a shaft ata first fixed position; and a second shaft support coupled to the frame,the second shaft support adapted to support a second portion of theshaft at a second fixed position. The tester also includes an actuatorcoupled to the second shaft support and adapted to displace the secondportion relative to the first portion to cause a lateral deflection inthe shaft; a sensor coupled to one of the first support, the secondsupport and the third support and adapted to output a signalcorresponding to a load force exerted by the shaft due to the lateraldeflection; a motor adapted to rotate the shaft when the shaftexperiences the lateral deflection; and a controller coupled to theactuator and the motor and adapted to control the deflection androtation.

In a further embodiment, the invention may be characterized as a methodfor use in testing a shaft comprising the steps: supporting a firstportion of a shaft at a first fixed position; supporting a secondportion of a shaft at a second fixed position; supporting a thirdportion of a shaft at a third fixed position; displacing the thirdportion relative to the first portion and the second portion causing adeflection in the shaft; outputting a signal corresponding to a loadforce exerted by the shaft due to the displacing; and controlling adisplacement of the shaft.

In another embodiment, the invention may be characterized as a methodfor use in testing a shaft comprising the steps of: supporting a firstportion of a shaft at a first fixed position; supporting a secondportion of a shaft at a second fixed position; laterally displacing thesecond portion relative to the first portion and the second portioncausing a lateral deflection in the shaft; outputting a signalcorresponding to a load force exerted by the shaft due to thedisplacing; rotating the shaft during the displacing step; andcontrolling the displacing and the rotating of the shaft.

In yet another embodiment, the invention may be characterized as amethod for use in testing a shaft comprising the steps: displacing afirst portion of a shaft relative to a second portion of the shaft tocause a deflection in the shaft; rotating the shaft when the shaft isexperiencing the deflection; measuring a load force exerted by the shaftdue to the deflection during the rotation; monitoring the measured loadforce over time; and generating a fatigue profile of the shaft based atleast in part on the monitoring step.

In a further embodiment, the invention may be characterized as a methodfor use in testing a shaft comprising the steps: displacing a firstportion of a first shaft relative to a second portion of the first shaftto cause a deflection in the first shaft causing a load force at a firstlevel to be exerted by the first shaft; rotating the first shaft whenthe first shaft is experiencing the deflection until the first shaftfails; determining a first length of time until the first shaft failed;displacing a first portion of a second shaft relative to a secondportion of the second shaft to cause a deflection in the second shaftcausing a load force at a second level to be exerted by the secondshaft; rotating the second shaft when the second shaft is experiencingthe deflection until the second shaft fails; determining a second lengthof time until the second shaft failed; and generating a fatigue lifeprofile based at least in part on testing the first shaft and the secondto extrapolate a fatigue life of additional shafts not tested.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of severalembodiments of the present invention will be more apparent from thefollowing more particular description thereof, presented in conjunctionwith the following drawings.

FIG. 1 is one embodiment of a free body diagram of a shaft testingdevice in accordance with several embodiments of the invention.

FIG. 2 is a schematic diagram of a control loop of a shaft testingdevice in accordance with some embodiments.

FIG. 3 is a shaft testing device in accordance with several embodimentsof the invention.

FIG. 4 is a perspective view of the bearing platform of the shafttesting device of FIG. 3 according to several embodiments.

FIG. 5 is a perspective view of the intermediate support of the shafttesting device of FIG. 3 according to several embodiments.

FIG. 6 is a shaft testing device in accordance with several embodimentsof the invention.

FIG. 7 is the shaft testing device of FIG. 6 in a loaded conditionaccording to one embodiment.

FIG. 8 is one embodiment of a free body diagram of the shaft testingdevice of FIGS. 6 and 7.

FIG. 9 is an enlarged view of a lower support assembly and a motorassembly and a linear assembly of the shaft testing device of FIG. 6according to one embodiment.

FIG. 10 is a top view looking at the x-y plane of a variation of thelower support assembly of FIG. 9.

FIG. 11 is a top view looking at the x-y plane of the upper supportassembly of the shaft testing device 600 of FIG. 6 according to oneembodiment.

FIG. 12 is a user interface for an application controlling a controllerof the shaft testing device of FIGS. 6-11 in accordance with oneembodiment.

FIG. 13 is a variation of the user interface of FIG. 12, and includingplots for the data collected and calculated according to one embodiment.

FIG. 14 is a graphical plot of load in lbs. vs. cycles of the datacollected until the shaft fails in accordance with one embodiment of theinvention.

FIG. 15 is a semi-log plot of load in lbs vs. revolutions at which theshaft failed at that load using a tester such as shown in FIGS. 1-5 orFIGS. 6-11 according to one embodiment.

FIG. 16 is a variation of the plot of FIG. 15 providing a semi-log plotof moment in lbs-in vs. revolutions according to one embodiment.

FIG. 17 is a flow chart of the steps performed in the operation of ashaft testing device in accordance with an embodiment of the invention.

FIG. 18 is a free body diagram of torsional fatigue shaft testing devicein accordance with further embodiments of the invention.

Corresponding reference characters indicate corresponding componentsthroughout the several views of the drawings. Skilled artisans willappreciate that elements in the figures are illustrated for simplicityand clarity and have not necessarily been drawn to scale. For example,the dimensions of some of the elements in the figures may be exaggeratedrelative to other elements to help to improve understanding of variousembodiments of the present invention. Also, common but well-understoodelements that are useful or necessary in a commercially feasibleembodiment are often not depicted in order to facilitate a lessobstructed view of these various embodiments of the present invention.

DETAILED DESCRIPTION

The following description is not to be taken in a limiting sense, but ismade merely for the purpose of describing the general principles ofexemplary embodiments. The scope of the invention should be determinedwith reference to the claims.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

Several embodiments of the present invention addresses the problemsdescribed above. In several embodiments, a shaft testing device ormachine and related methods are provided to test the characteristics ofa shaft or similar elongate structure that is intended to deflect or tobend in use. For example, a shaft is deflected to determine the breakingpoint of the shaft. In other embodiments, the shaft is deflected aboutvarious rotational locations of the shaft. In some embodiments, theshaft is deflected while being rotated to test for breakage or togenerate a profile of the fatigue or fatigue life of the shaft.Generally, in some embodiments, when testing the fatigue life of ashaft, the shaft is maintained in a deflected state while being rotatedover time while measuring load forces exerted by the shaft at one ormore points of the shaft and/or calculating moments generated at one ormore locations of the shaft. This data may be analyzed over time and aprofile can be generated of the fatigue life of the shaft, for example,the ability of the shaft to withstand intended deflection at variouscircumferential locations over time. In some embodiments, the testersand methods provided are safe and quiet to use, can be performedquickly, and can be used in an automated fashion without humansupervision. Several embodiments are also safe in that they are notballistics tests.

In some embodiments, a shaft testing device tests shaft fatigue at up to360 degrees of a golf shaft, whereby full cycles of tensile andcompressive loads are applied to the shaft. This gives a betterunderstanding of the shaft's structural integrity at multiple locationsof the circumference to throughout the entire circumference of the shaftwithout having to worry about how the shaft is oriented during testing.Furthermore, in some embodiments, the system tests the bending fatigueof a shaft without a golf head, or any reasonable facsimile, attached orbonded to the shaft.

Referring to FIG. 1, a free body diagram of a shaft testing device isshown in accordance with some embodiments of the present invention. FIG.1 depicts loads on a shaft 102 under test, for example, the loads applya moment at the tip end that mimic the moment on a shaft during a golfswing when the shaft 102 is deflected between two portions, the momentresults in a deflection shape that mimics the deflection shape occurringduring an actual golf swing. The shaft 102 is clamped by a butt support101 at a butt end (illustrated at point C), with an intermediate support104 at point B and two tip supports 106, 108, the tip supports 106, 108mimicking a shaft location in a golf head. That is, in some embodiments,the tip support 106 is intended to be located at the location at thepoint where the shaft first enters a hosel or club head. The tip support106 is illustrated at point A and the tip support 108 is illustrated atpoint D. In one embodiment, the tip supports 106 and 108 are locatedapproximately two inches apart from one another (along the z axis), withthe tip support 106 absorbing the majority of the load at the tip whenthe shaft tip end is displaced relative to the shaft butt end. Forexample, in the illustrated embodiment, the shaft tip end is laterallyor linearly displaced along the x axis relative to the butt end of theshaft, such that the shaft is deflected about the intermediate support104. The intermediate support 104 is adjustable in a vertical direction(e.g., z axis) in order to accommodate different types of shafts atdifferent lengths and varying loading conditions. As depicted by thearrow E around the shaft tip end, in some embodiments, the shaft testingmachine rotates the shaft 102 while the shaft is in the bent ordeflected (loaded) position illustrated. In some embodiments, theintermediate support 104 is located toward the shaft tip end of theshaft 102 in order to focus the majority of the bending stress towardthe tip end of the shaft (i.e., the portion of the shaft thatexperiences the majority of the bending stresses in actual use in a golfclub). Thus, in one form, the intermediate support 104 is located lessthan 50% of the length of the shaft toward the tip end, in another form,less than 40% of the length of the shaft toward the tip end, while inanother form, less than 30% of the length of the shaft toward the tipend.

The supports 101, 104, 106 and 108 rigidly fix the shaft in an x, y, zspace but allow the shaft to rotate about the z axis. Furthermore, inthe illustrated embodiment, as will be made more clear in the followingdiscussion, the tip supports 106 and 108 are movable about the x axis tolaterally displace or deflect the tip end of the shaft relative to thebutt end of the shaft and the portion of the shaft contacting theintermediate support 104. In some embodiments, the tip end of the shaft102 is rigidly fixed to a sleeve which is held in position by the tipsupports 106, 108.

Referring to FIG. 2, a basic schematic of a control loop of a shafttesting device 200 is shown in accordance with one embodiment of thepresent invention.

In operation, the tip of the shaft 102 is loaded into a bearing block202 (which implements tip supports 106 and 108) while the butt end ofthe shaft is inserted into a chuck 204 (implementing the butt support101 and coupled to part of a rotary motor 206) and then manuallytightened. The chuck 204 holds one portion (in this case, the butt end)of the shaft in a fixed x, y, z position and also holds the shaft sothat it can not rotate within the chuck 204. A bearing platform 208supporting the bearing block 202 is then raised or lowered along the zaxis in order to make the top of the bearing block 202 flush with whatwould be the top of the hosel in a golf club. That is, the portion ofthe shaft at the top of the bearing block 202 should be the location ofthe shaft that would be where the shaft enters the hosel (i.e., thebearing block 202 mimics the hosel or club head). In other words, thesystem mimics the shaft/club system that is seen in the field. Theheight of the bearing platform 208 may be adjusted within the frame,e.g., the bearing platform 208 is slidingly coupled to the frame. Theshaft 102 is then horizontally or laterally displaced, e.g., about the xaxis in the illustrated embodiment, according to either a targetdistance or load relative to the shaft butt end. To displace the shafttip end, the bearing block 202 is attached to a linear bearing guide 212that is horizontally or laterally displaced along a stationary linearguide rail 214. Thus, the tip end of the shaft is linearly displacedrelative to the stationary butt end at the chuck 204/motor 206. In someembodiments, the bearing block 202 is manually displaced. In someembodiments, the bearing block 202 displacement is automated; that is,the bearing block is moved along the linear guide rail 214 in responseto a command from a controller 216. In some embodiments, a brake (notshown in FIG. 2) locks the block into place. A load cell 218 is coupledto the bearing block 202 (via a load cell coupling) to measure the loador force applied to the bearing block 202 by the shaft due to thedeflection. The load cell 218 outputs an electrical signal that isamplified (e.g., by amplifier 220) and input to the controller 216and/or computer, the electrical signal corresponding to the force orload. As it is used throughout this specification, the term load cellmay generically be referred to as a sensor.

Once deflected, while being maintained in the deflected state, the shaft102 is caused to rotate by the motor 206 under control of the controller216. In some embodiments, a user inputs a target frequency at which theshaft rotates under test. In some embodiments, a user inputs athreshold/trip point that allows the device or machine to automaticallystop when the load drops below the prescribed threshold. For example, ifthe shaft were to fail (break), the measured load (from the load cell218) would drop below the threshold, and the rotary motor 206 would bedisabled to stop rotation. Thus, in one form, the output of the loadcell 218 is used by the controller 216 controlling the operation of therotary motor 206. In some embodiments a user initiates testing (shaftrotation) by interacting with the human machine interface. In someembodiments, a user initiates testing by interacting with a PC coupledto the system (i.e., the controller includes or is coupled to a personalcomputer). In some embodiments, the system runs until manuallyterminated. In alternative embodiments, the system is automaticallyterminated when failure occurs (a shaft breaks) or a stopping eventoccurs. A stopping event is, for example, an elapse of a user-selectedamount of time, a change in load, or other event in response to whichthe testing will terminate.

While the shaft testing machine 200 is running (i.e., the shaft isdeflected and rotated), the load measurements and corresponding rotarylocation measurements or readings are output to the controller 216 to beprocessed (or further output to a computer). In some embodiments, themotor 206 includes a rotary encoder in order to determine (and output)its circumferential location at all points in time. Load cellmeasurements are correlated to circumferential positions to output,display, and/or process load measurements at multiple or allcircumferential locations about the shaft, depending on the resolutionof the rotary encoder. In some embodiments, the user can program thefrequency at which to record and/or display load measurements and alsoprogram the number of locations about the circumference to record and/ordisplay the load measurements.

Reference is now made to FIGS. 3-5. FIG. 3 illustrates a shaft testingdevice 300 in accordance with several embodiments of the invention. FIG.4 illustrates the bearing platform and FIG. 5 illustrates theintermediate support of the shaft testing device of FIG. 3 according toseveral embodiments. The shaft testing device operates generallyaccording to the description of FIGS. 1-2 and is presented to provide anexample of and further description of a shaft testing device or machineaccording to several embodiments.

The shaft testing device 300 for testing the shaft 102 includes a frame320, the chuck 204, the motor 206 and the bearing platform 208 includingthe bearing block 202, the linear bearing guide 212, the load cell 218,a load cell bearing guide 302, linear guide rails 214, stoppers 304, anda load cell coupling 306. The device 300 also includes the intermediarysupport 104 including wheels 308, 310 and support brackets 312, 314rigidly mounted to the frame 320. The device 300 also includes thecontroller 216, which in the illustrated embodiment has a humaninterface. Embodiments of several of the components of FIGS. 3-5 aredescribed below.

The motor 206 is coupled to the chuck 204 and causes rotation of theshaft 102 about the z axis under deflection. In some embodiments, thesystem uses a NEMA 34 single stack stepper motor. In one embodiment, themotor 206 rotates the chuck 204 that holds the butt end of the shaft,thus rotating the entire shaft. The motor 206 controls partial and/orfull rotations. The motor 206 also has the capability to be easilymanipulated using the controller 216 and can run for extended periods oftime under nominal loads.

In some embodiments, the feedback loop is a closed system defined by thecontroller 216, the motor 206, the load cell 218 and the load cellamplifier 220. In some embodiments, the controller 216 includes a HumanMachine Interface (HMI), whereas in other embodiments, the controller iscoupled to a computer running software that allows a human to programand control the controller. Under test, in one embodiment, the tip endof the shaft is manually displaced relative to another portion of theshaft (e.g., along the x axis), which puts a load on the shaft at pointsA, B and C (see FIGS. 1 and 2). The peak load is typically located atPoint A.

In some embodiments, the load at point A is measured by the load cell218 (as a load exerted by the bearing block 202 on the load cell 218),amplified to 0-5V DC and sent to the controller 216. The controller 216receives a signal from the load cell amplifier 220 within the prescribed0-5V analog input range. This information is converted into binaryunits, which in turn is calibrated into a load (lbs). The binary unitsare directly proportional to the capacity of the load cell 218. In someembodiments, for example, the capacity of the load cell is 500 lbs. InFIG. 3, the controller 216 is illustrated as a small input device withinput keys and a display, and including a controller or programmablelogic controller (PLC) for recording, processing and/or outputting loadand angular position measurements to a computer.

In the event of shaft breakage the controller 216 is programmed to stopthe motor 206 when the load goes below a certain prescribed threshold.

As illustrated in FIGS. 1 and 2, the shaft testing device 300 providesthree boundary points at A, B and C. Point A is defined at the bearingblock 202. In the embodiment illustrated in FIG. 2, the bearing block202 holds the tip end of the shaft. The shaft threads or fits throughthe bearing block and the bearing block is laterally displaced (e.g.,along the x axis) relative to the butt end of the shaft (thus, bendingthe shaft). In preferred form, as illustrated, the shaft is bent aboutpoint B at the intermediate support 104 to place the majority of thebending stress on the tip end of the shaft. When testing is initiated,the shaft is caused to rotate within the bearing block 202. That is, insome embodiments, the portion of the bearing block 202 that contacts theshaft is rotatable within the bearing block. In one embodiment, thebearing block 202 contains two bearings stacked 2 inches apart in ablock of Aluminum. It is noted that the bearing block may be genericallyreferred to as a holder or a support that holds or supports a portion(e.g., the tip end) of the shaft in a fixed position (e.g., fixed butadjustable x-y-z locational position while allowing rotation of theshaft about the z axis). It is understand that this support or holdermay be located at the tip end of the shaft or at another portion of theshaft.

In embodiments employing an intermediate support 104, point B is definedby the intermediate support. The intermediate support 104 is adjustablein a vertical direction along the z axis (e.g., along a portion of theframe) in order to accommodate different types of shafts at differentlengths and to simulate varying loading conditions depending on thecharacteristics to be tested. Generally, the intermediate support 104provides a rigid lateral support of the shaft while allowing the shaftto rotate. In some embodiments, low friction wheels 308 and 310 arecoupled to a frame (via one or more supports or brackets 312 and 314)and are used as the intermediate support. One of ordinary skill in theart will recognize that there are numerous low friction rotary devicesthat can support a shaft while allowing it to rotate and minimizecontact friction between the shaft and the wheel. In some embodiments,depending on the application of the shaft being tested, no intermediatesupport is provided. However, in many applications of testing a golfshaft, it is desired to focus the bending forces toward the tip end ofthe shaft; thus, the intermediate support 104 is provided. In someembodiments, the intermediate support 104 is not used; however, furtherdeflection (lateral displacement of the shaft and tip ends) is needed toachieve the same deflection or load. It is noted that the intermediatesupport 104 may be generically referred to as a holder or a support thatholds or supports a portion (e.g., an intermediary portion in betweenthe tip and butt ends) of the shaft in a fixed position (e.g., fixedx-y-z locational position while allowing rotation of the shaft about thez axis).

Point C is defined in some embodiments by the chuck 204. In theillustrated embodiment, the chuck 204 holds one portion of the shaft(e.g., the butt end) in a fixed location, but causes rotation of theshaft. In some embodiments, the chuck 204 is a standard drill presschuck that opens up to accept a 0.620″ butt end of a golf shaft. In someembodiments, it also has a threaded end, as opposed to an arbor on alathe chuck. It is noted that the chuck may be generically referred toas a holder or support that holds or supports a portion (e.g., the buttend) of the shaft in a fixed position (e.g., fixed x-y-z locationalposition and fixed but adjustable rotational position).

The frame 320 rigidly couples the various components together andmaintains the various components at a fixed orientation. In someembodiments, the frame 320 is made of extruded aluminum for itsstructural members. The extruded aluminum material has advantages tothat of a conventional welded steel frame in weight, cost and overallmodularity. In some embodiments, a multitude of attachments andfasteners are coupled to the extruded aluminum frame. Generally, theframe provides a structure to rigidly hold to which supports points A,B, C relative to each other. It is understand that the frame maycomprise one or more frames or one or more frame members or otherstructure to maintain points A, B, C in a fixed (although adjustable)relationship with each other.

In the embodiment of FIGS. 3-5, the chuck 204 rigidly holds or supportsthe butt end of the shaft in an x-y-z position and in a rotary position,the bearing block 202 rigidly holds or supports the tip end of the shaftin an x-y-z position but does not rigidly hold the tip end in a rotaryposition. In other embodiments, the butt end is rigidly held but allowedto rotate while the tip end is rigidly held in both position androtation (tip end being coupled to the rotary motor). In otherembodiments, both the tip end and the butt end extend into and/orthrough bearing blocks that rigidly hold the end in positional location,but allow rotation. In this case, one end of the shaft (e.g., extendingthrough a bearing block) is coupled to a rotary motor or another portionof the shaft is coupling to a rotary mechanism, such as a belt drivecoupled to a rotary motor.

As shown in FIGS. 3-5, some embodiments of the frame are rectangularsuch that a shaft is disposed vertically within the frame. Theintermediate support 104 is coupled to a vertical aluminum columnsituated inside the frame, the vertical aluminum column coupled to theframe by aluminum arms.

In some embodiments, linear ball bearings are used to displace thebearing block 202, e.g., laterally displace the bearing block 202relative to the chuck 204). In one example, the return force on Point Ais about 115 lbs. This force makes it difficult to manually displace thebearing block 202 along the x axis with a shaft inserted. There is alsoa large moment/torque that is created (a moment is defined as a forceover a distance) upon displacement. This force literally wants to “peel”the bearing block 202, as well as the linear bearing guides 212 and 218off of the rails 214. Because of this, the linear bearing guides 212,218 have a robust static/dynamic load capability in some embodiments. Insome embodiments, the load capability of the linear bearing guides is 55kN. As illustrated in the example implementation of FIGS. 3-4), thebearing block 202 and the load cell 218 are mounted and move togetheralong two linear guide rails 214. Once in the proper position to causethe desired deflection, the bearing block 202 and the load cell 218 arelocked into position on the linear guide rail 214, e.g., using lockingbrackets or stoppers 304. The load cell 218 is coupled to the bearingblock via a load cell coupling 306. In some embodiments, the movement ofthe bearing block/load cell may be electronically controlled using anelectromechanical actuator.

In several embodiments, the load cell 218 is a transducer, whichconverts force into a measurable electrical output. Although there aremany varieties of load cells, strain gage based load cells are the mostcommonly used type. Strain Gauge load cells convert the load acting onthem into electrical signals. The gauges themselves are bonded onto abeam or structural member that deforms when weight is applied. In someembodiments, four strain gages are used to obtain maximum sensitivityand temperature compensation. Two of the gauges are usually in tension,and two in compression, and are wired with compensation adjustments.When weight is applied (the shaft is deflected), the strain changes theelectrical resistance of the gauges in proportion to the load.

In some embodiments, a 500 lb capacity load cell is used along with anoutput amplifier (not shown in FIG. 3). A load cell with this capacityis appropriate because the known load does not exceed 500 lb. Theamplifier increases the signal strength to an acceptable level (0-5V DC)so that the controller can read it. The load applied to a shaft isdependent upon many factors including the thickness and strength of theshaft and the amount of displacement.

In some embodiments, there are a plurality of intermediate supports. Forexample, in some embodiments there is one additional intermediatesupport than is shown in FIG. 3. The intermediate supports may bepositioned to provide a support or force on the shaft in the same ordifferent directions. For example, in embodiments with two intermediatesupports, the supports are located on opposite sides of the shaft indifferent vertical positions from each other and apply a force on theshaft in opposite directions. Both intermediate supports may be adjustedup and down vertically in order to accommodate different types of shaftsat different lengths and varying loading conditions. In someembodiments, intermediate supports are supported by aluminum verticalcolumns supported by aluminum arms coupled to the frame. In someembodiments, a load cell may be coupled to one or more of theintermediate supports to provide additional load measurements at variouspoints of interest along the shaft.

In some embodiments the load cell measures a load at the butt end of theshaft instead of in addition to load measurements taken at or near thetip end. In some embodiments, the butt end of the shaft rotates within abearing block while the tip end of the shaft is fixedly held by a clampor chuck. In some embodiments, the motor is located on the bottom of theframe. In some embodiments, the motor rotates a chuck holding the tipend of the shaft.

The fatigue testers described herein may be used with a variety ofdifferent shafts, such as sports implements (e.g., golf shafts, polevault shafts, etc.) or any or shaft that is intended to deflect or bendin use. In some embodiments, the testers and methods described hereinare used to test the deflection characteristics of a shaft, for exampleto test failure (breaking point). In other embodiments, the testers andmethods are used to test fatigue life in deflection (e.g., bended). Forexample, the shaft is loaded (deflected to simulate use) for periods oftime. Over time, fatigue characteristics can be generated from loadmeasurements to determine the deflection endurance or fatigue of ashaft, for example, for quality control purposes.

In some embodiments, data from a load cell is sent to a PC (not shown)and a representation of the data displayed. Data relating to the load ata plurality of points around the circumference of the shaft is sent tothe PC. Data relating to the number of revolutions of the shaft is sentto the PC. In some embodiments, the moment (force over a distance, i.e.the length of the shaft) is calculated at the PC. In some embodimentsfatigue life of a shaft may be predicted based upon data gathered at thePC.

In one embodiment, the invention may be characterized as a method fortesting a shaft comprising holding a first portion of a shaft in a firstholder; holding a second portion of the shaft in a second holder; anddisplacing the second portion of the shaft relative to the firstportion. In a further variation, the shaft is rotated while beingdisplaced.

In alternative embodiments, a sleeve is bonded to the tip end of theshaft to simulate an actual golf head hosel. Since the shaft tip andhosel are in contact in a shaft in use, the golf head hosel's design cangreatly influence shaft life. In this embodiment, the bearing block 202is configured to receive the sleeve, holding the tip end of the shaftand the sleeve in an x, y, z location, but allowing both the tip end andthe sleeve to rotate within the bearing block.

Referring next to FIG. 6, a shaft testing device 600 is illustrated inaccordance with several additional embodiments of the invention. Theshaft testing device 600 includes a frame 602 having a base support 604rigidly fixed within the frame 602 and having a linear guide rail 606extending upwardly therefrom. The base support 604 includes a motorassembly 608 and electronics. An upper support assembly 610 and a lowersupport assembly 612 are rigidly coupled to the linear guide rail 606 atdifferent vertical locations. The upper support assembly 610 and thelower support assembly 612 may be adjusted to different heights alongthe linear guide rail 606 to accommodate different length shafts and toprovide for different deflection testing conditions. For example, thelinear guide rail 606 may be provided with a series of spaced holes 614through which a pin lock inserts or through which a stem of a threadedknob inserts to hold the support assembly at a given vertical height.This height may be manually adjusted as needed. For example, asillustrated, the upper support assembly 610 may be positioned with afirst vertical range 616 and the lower support assembly 612 may bepositioned with a second vertical range 618.

The base support 604 also includes a shaft holder 620 (which may also bereferred to as a shaft support). In the illustrated embodiment, theshaft holder 620 receives the tip end of the shaft 102. In preferredform, the tip end of the shaft is bonded within a shaft sleeve that isused to simulate the shaft—hosel interface, preferably using the samebonding agent as would be used between a shaft and a hosel. Accordingly,the shaft holder 620 is configured to receive the sleeve and rigidlyhold the sleeve (i.e., portion of the shaft) in a fixed x, y, z androtation position within the shaft holder 620. In one version, a screwor axle is moved through an opening in the support holder 620 and thesleeve to fixedly engage the tip end of the shaft with the shaft holder620. The shaft holder is coupled to a motor drive shaft 622 which isrotationally coupled to a rotary motor 624. A cooling fan 626 is used toremove excessive heat generated by the motor 624. The base support alsohouses various electronics, such as a controller (not specificallyillustrated) and rotary and linear actuator components. In thisembodiment, the controller does not include a human machine interface,but electrical connections to a computer 628. In one embodiment, thecontroller is a programmable logic controller (PLC).

The shaft 102 is also supported in an upright position through contactwith the upper support assembly 610 and the lower support assembly 612.In the illustrated embodiment, the upper support assembly 610 includesguide wheels 630 that engage one side (e.g., left side in the view ofFIG. 6) of the shaft, while the lower support assembly 612 includesguide wheels 632 that engage an opposite side (e.g., right side in theview of FIG. 6) of the shaft. FIGS. 9-11 more clearly illustrate theupper support assembly 610 and the lower support assembly 612. The motorassembly 608 is mounted to a linear actuator assembly 634 including alinear motor 635 and a linear actuator 637 moveable about guide rails636 such that motor assembly 608 including the shaft holder 620 moved tolinearly moved along the x axis (see arrow 638) relative to thestationary upper and lower shaft supports 610, 612. The movement of theshaft holder 620 causes a deflection of the shaft between points 1, 2and 3, labeled as P1, P2 and P3. The illustration of FIG. 7 shows themotor assembly in a loaded position causing the resulting deflection ofthe shaft 102. FIG. 8 illustrates a free body diagram of thisdeflection.

Similar to other embodiments described herein, the shaft is deflected inorder to perform one or more tests on the shaft. In some embodiments,once deflected, the shaft is rotated, either partially or entirely andrepetitively about the z axis (resulting in a moment 802 generated asillustrated in FIG. 8). The speed and direction of the rotation can becontrolled by user defined parameters entered at the computer 628. It isnoted that when the shaft is deflected, the shaft is securely held inposition between the wheels 630 and 632 and the shaft holder 620 eventhough the wheels only engage one side of the shaft, respectively. Thewheels maintain the potion of the shaft contacting the shaft supportassembly in an x, y, z space, but allow for the shaft to rotate aboutthe z axis. In one embodiment, the wheels 630, 632 are low frictionsrotary devices that provide little resistance to rotation, but hold theshaft in location. The holder rigidly engages the tip end of the shaftin order to cause the shaft to rotate. It is noted that in oneembodiment, the moment 802 is generated as Moment=(P2*L2)−(P1*L1), whereP1 and P2 are the load cell values at locations P1 and P2, and L1 is thedistance along the z axis from P3 to P1 and L2 is the distance along thez axis from P3 to P2.

According to several embodiments, the shaft testing device 600 includesan upper load cell 1110 and a lower load cell 912 (best seen in FIGS.9-11). In this embodiment, a load cell is not used at the shaft holder620 since the moment just above the shaft holder 620 can be calculatedbased on the load data at P1 and P2 given the known physicalrelationship and parameters. Each load cell measures the load as theshaft is rotated. The data output from the load cells is input to thecomputer 628 for processing and analysis.

Referring to FIG. 9, an enlarged view of the lower support assembly andthe motor assembly and linear assembly of the shaft testing device 600of FIG. 6 is illustrated. The lower support assembly includes brackets902, 904, 906 and 908, wheel support 910, the load cell 912, and an arm914. Bracket 902 couples to the linear guide rail 606. Brackets 902, 904and 906 form a “C” about the shaft 102. Bracket 908 couples the wheelsupport 910 to the load cell 912. The wheel support 910 supports thewheels 632 and permits free rotation. The arm 914 serves as a guide andsafety measure if the shaft fails under load. Also clearly seen in FIG.9 is the shaft holder 620 of the base support 604. The shaft holder 620coupled to the motor shaft through a hole on in plate 916 such that theshaft holder 620 rotates relative to the stationary plate 916. The plate916 rigidly couples to the linear actuator 637, which moves linearlyabout the linear guide rails 636. As the linear actuator 637, plate 916and the shaft holder 620 move in the x direction (e.g., to the right inFIG. 9), the shaft is deflected or loaded about the lower supportassembly 612 and the shaft holder 620. Load measurements are taken bythe load cell 912. A top view in the x-y plane is shown of a variationof the lower support assembly in FIG. 10 and illustrating a load cellcoupling 1002 and variation of the arm 1004. The lower support assemblyof FIG. 10 includes a knob that can be tightened to secure the lowersupport assembly to the guide rail 606.

Referring to FIG. 11, a top view is shown of the upper support assembly610 of the shaft testing device 600 of FIG. 6. The upper supportassembly 610 includes brackets 1102, 1104, 1108, wheel support 1114, theload cell 1110, load cell coupling 1112 and an arm 1106. Bracket 1102couples to the linear guide rail 606. Brackets 1102 and 1104 provide themain support from the assembly 610. Bracket 1108 couples the wheelsupport 1114 to the load cell 1110 via the load cell coupling 1112. Thewheel support 1114 supports the wheels 630 and permits free rotation.The arm 1106 serves as a guide and safety measure if the shaft failsunder load. Load measurements are taken by the load cell 1110 and outputto the computer 628 for processing.

It is noted that in some embodiments, the shaft testing device onlyincludes one support assembly, instead of both an upper and lowersupport assembly 610, 612. In this case, the shaft holder 620 displacesone portion of the shaft (e.g., the tip portion) relative to the otherportion of the shaft held by the other shaft support assembly. Oncedisplaced, the shaft may be rotated while taking load measurements.

In accordance with one or more embodiments, the shaft testing devicesdescribed herein may be operated in one or more modes. For example, theshaft testing device may operate in a ‘static bend mode’ in which aportion of the shaft is deflected until the shaft breaks or fails. Forexample, referring to the embodiments of FIGS. 6-11, the motor assembly608 is laterally moved along the x axis in defined increments causing adeflection of the shaft about P1, P2 and P3 until the shaft fails. Fromthis test, it can be determined at what load and displacement the shaftwill fail. In this embodiment, the shaft is not rotated. In a ‘staticbend with rotation mode’, one portion of the shaft is incrementallydeflected relative to another portion of the shaft. At each incrementamount of deflection, the shaft is completely rotated at a slow speed tosee if the shaft will fail. If the shaft does not fail, the portion ofthe shaft is further deflected in the next incremental amount androtated again. The process is repeated until the shaft fails. For thistest, angular orientation of failure is determined. In a ‘fatigue testmode’, one portion (e.g., the tip end) of the shaft is deflected (e.g.,laterally along the x axis) relative to another portion of the shaft(e.g., the butt end of an intermediate portion). Once deflected to adesired load, the shaft is continuously and repetitively rotated at adefined number or revolutions per second for a desired number of cyclesor until the shaft fails. In this manner, a user can determine how manycycles before the shaft fails under different load conditions.

During one or more of the test modes, load cell data, and linear androtary encoder measurements are output to the controller 216 or computer628 for processing. Load cell data may be taken at or adjacent one ormore locations of the shaft supported by a shaft support or shaftholder, such as those described herein. In preferred form, load celldata is collected at the portion of the shaft at or near the tip end,which in use is the area of the shaft that experiences the most loadingforces. Additional load cell data may be obtained from other portions ofthe shat, such as the upper and lower support assemblies 610 and 612 orthe chuck 204 and intermediate support 104. Other data output to thecomputer may include rotation speed, the number of revolutions orcycles, a moment calculated at a given load location, etc.

Referring next to FIG. 12, a user interface is shown for an applicationrunning on the computer 628 and controlling a controller of the shafttesting device of FIGS. 6-11 in accordance with one embodiment. It isunderstood that the user interface is generated and caused to bedisplayed by a software application stored on the computer or remotelystored but executed at least in part on the computer. In one embodiment,the application was developed using by LabView, a well knowncommercially available software development tool. The user interface1200 includes parameters that may be entered by an operator, e.g.,within fillable fields. Data under the test report region 1202 includesbasic information entered by the use including operator, customer,model, part number, type of shaft, flex (e.g., level of shaftstiffness), and configuration.

The static test region 1204 includes parameters when performing thestatic bend mode and the static bend with rotation mode. TheIntervalDist (mm) field allows the user to define the spacing betweenlateral displacements of one portion of the shaft relative to anotherportion in millimeters. In other words, it defines the distance betweendisplacement steps. The RotSpeed (RPS, revolutions per second) definesthe rotational speed. This value will be set to ‘0’ in the event a‘static bend mode’ test is performed, but will be set to a value whenperforming a ‘static bend with rotation mode’ test, which is preferablya value less than 1.0 to slowly rotate the shaft. The LoadSpeed (mm/s)field defines the velocity of the loading or deflection. ThePreLoadSpeed (mm/s) field defines the speed of linear actuator movementwhen moving to initially engage the shaft prior to causing a deflection.The MinimumLoad (lb) field defines the minimum load or preload that isapplied prior to deflection. The HoleNoofTopLoadcell field defines thevertical height of the upper support assembly 610 and in particular, theload cell 1110. In particular, it indicates which hole 614 the uppersupport assembly engages. Similarly, the HoleNoofBtmLoadcell fielddefines the vertical height of the lower support assembly 612 and inparticular, the load cell 912. In particular, it indicates which hole614 the lower support assembly engages. The upper holes are labeled bynumber and the lower holes are labeled by letter to avoid confusion.

The fatigue test region 1206 includes parameters when performing thefatigue test mode. The NoOfCycles field defines how many completerevolutions the shaft will rotate under load, typically, this numberwill be several thousand cycles. If the number is ‘0’, the shaft willrotate indefinitely until failure or until the user terminates the test.The RotSpeed (RPS, revolutions per second) defines the rotational speed.This value will preferably be a value greater than 1.0 to quickly rotatethe shaft. The RotAccTm (ms) field defines the time for the motor 624 toreach the user defined rotation speed, i.e., it defines the accelerationof the rotation. The TargetLoad (lb) field defines the load cell valuethat should be reached by the deflection of the shaft. For example, thetip end of the shaft will be deflected until the load cell at the shaftholder 620 reaches the target load, e.g., 20 pounds, The TripPoint (lb)field defines the load measurement in order for the system to declare afailure. For example, in operation, the shaft will be deflected to aload of 20 pounds and rotated. After many thousands of rotations, theshaft will fail, which will be indicated by a reduction in the load cellmeasurement after the point of failure. In this example, the defaulttrip point is set at 0.5; however, in most cases, the trip point shouldbe set to about 10 lbs less than the target load. Thus, in one exampleof FIG. 12, the trip point would be set to 10 lbs so that when themeasured load drops to 10 or fewer lbs, the system declares a failure.Like the static test field 1204, the HoleNoofTopLoadcell field and theHoleNoofBtmLoadcell field define the vertical height of the load cellsof the upper and lower support assemblies 610 and 612.

The indicator region 1208 provides the status of the operation of thesystem, such as indicating the number or rotations thus far, the maxload, the linear or lateral displacement or deflection. This region 1208also includes lights to indicate if the shaft testing device is ready,an alarm condition exists, an electronic stop occurred, that a doorclosing off the frame is closed and when there is no shaft present.

In some embodiments, the user interface 1200 includes real time plots ofthe data collected during a given test. Region 1210 provides the loadcell measurements from the load cell 1110 of the upper support assembly610 as load values vs. number of cycles. Region 1212 provides the loadcell measurements from the load cell 912 of the lower support assembly612 as load values vs. number of cycles. Region 1214 provides acalculated moment at a portion of the shaft proximate the point of entryof the shaft into the shaft holder 620, e.g., just above the shaftholder 620 vs. the number of cycles. This value is calculated based onthe measured load cell values and defined relationship between thevarious components. It is well within the ability of one of ordinaryskill in the art to calculate such a moment. For example, in oneembodiment, referring to the free body diagram of FIG. 8, the moment 802is calculated as (P2*L2)−(P1*L1).

FIG. 13 illustrates one sample fatigue test mode including plots for thedata collected and calculated. In this test, the shaft is laterallydeflected to a load of 65 lbs and rotated at 32 revolutions per second.The resulting data is plotted as lines 1302, 1304 and 1306,respectively. So far in the test, no failure has occurred. A failurewould be declared by the system in the event the load measurements atthe shaft holder 620 drop to 55 lbs. This level will not result in theshaft breaking, but results in a breakdown in the rigidity of the shaftto the point that the shaft will not perform as expected.

According to several embodiments, load cell measurements and/orrotational (and/or angular) position measurements are output to thecontroller and/or computer for display, storage and/or processing. Insome embodiments, the load of a shaft is measured and plotted over time(in terms of revolutions at a certain rotation frequency). For example,TABLE 1 below shows the first ten entries of data collected by oneembodiment of a tester (such as illustrated in FIGS. 1-5) testing a golfshaft being rotated at 15 revolutions per second (15 rps) with aninitial lateral deflection of the tip end relative to the butt endproducing a load of approximately 27 lbs. Generally, load measurementsare recorded approximately every 300 cycles (revolutions). In thisexample, the measurements are not taken at exactly the samecircumferential location; however, in other examples measurements may betaken at the same circumferential location or locations about the shaft.

TABLE 1 Load (units) Load (lbs) Cycles 570 27.832 0.038 544 26.807299.922 565 26.172 600.572 565 26.514 901.215 539 26.709 1201.858 54526.611 1502.507 561 27.49 1803.162 538 27.002 2103.802 541 26.8072404.452 563 26.758 2705.1 . . . . . . . . .

FIG. 14 illustrates a graphical plot of load in lbs. vs cycles (numberof revolutions) of the data collected until the shaft fails (i.e.,breaks, the load drops to zero). For example, the plot of FIG. 14 is afiner resolution example of the plots of regions 1210 and 1212 of FIGS.12 and 13. It is noted that to generate the data for FIG. 14, TABLE 1continues for thousands of cycles (only the first tens entries beingillustrated).

As can been seen, line 1402 represents the actual data collected and inthis case, this data varies within 2 lbs until the shaft fails at justunder 300,000 revolutions. Line 1404 is a moving average line reflectingthe average of 10 measurements. It is apparent that differently designedshafts (different materials, stiffness, etc.) will have a different loadprofile, while in some embodiments, it is desired that different shaftsof the same design will have the same profile. In some embodimentsincluding one or more of the embodiments described throughout thisspecification, the data is processed, saved and output for display for auser, for example, using a computer having a processor, memory andsoftware, firmware, or other machine readable instructions to processand display the data. In some embodiments, the information representedin TABLE 1 and FIG. 14 is used for a variety of purposes. For example,it is possible to test a shaft and determine its fatigue life, andadditionally compare it relative to other shafts. It may also bepossible to analyze the data to determine points in time that indicatethe approaching failure of a shaft (perhaps a sudden change in loadprior to failure). Similar to the plot of region 1214, the plot couldalternatively be a calculated moment vs. number of revolutions.

In some embodiments, a shaft is tested under different loads. Referringnext to FIG. 15, a semi-log plot is shown of load in lbs vs revolutions(in this case, at 15 rps) at which the shaft failed (broke) at that loadusing a tester such as shown in FIGS. 1-5 or FIGS. 6-11. For example, afirst shaft is deflected or bent to a load of approximately 42 lbs andthen rotated until the shaft fails. In this case, the shaft failed atpoint A at about 200 revolutions (the x axis is in log scale). Thensecond shaft (which should be identical to the first shaft) is loaded toabout 25 lbs (i.e., deflected less than the first shaft) and rotateduntil it failed at point B at about 10,000 revolutions. A third shaftloaded to about 21 lbs failed at point C also at about 10,000revolutions. A fourth shaft loaded to about 15 lbs failed at point D atabout 50,000 revolutions. And a fifth shaft loaded to about 13 lbsfailed at point E at about 100,000 revolutions. Based on thisinformation, a straight line 1502 is drawn based on points A-E whichclosely approximates the fatigue life of that particular shaft at anyload. Statistically, the R² value approximates how closely line 1502matches the measured data, and in this case, R²=0.9825, where 1.0 isideal. Using this information, one can estimate what the expectedfatigue life of a shaft will be under certain loads. This informationcan be helpful in determining if a particular shaft is well suited foran intended application (intended deflection or load) and intendedlifetime of the shaft in use. While FIG. 15 illustrates only 5 testpoints, it is possible to generate such a line (e.g., load vs fatigueprofile) from fewer or more than the 5 points. For example, using aplurality of identical or substantially identical shafts and a testermachine such as disclosed herein, it can be determined at what load theshaft will statically fail (no revolutions), and then begin testing forfatigue at certain percentages of that static failure load. For example,if it is determined that a given shaft statically fails with a 50 lbdeflection load (i.e., the shaft is deflected without rotation until itfails), then the first shaft is tested under load and rotation at 90% ofthat load, the second shaft at 80% of that load, the third shaft at 70%of that load, and so on. It is noted that these percentages are by wayof example, and other percentages and techniques may be used todetermine what load test points would be used in generating a profile(e.g., line 1502).

Furthermore, in cases where the R² value indicates a good fit (such aswhere R²=0.9825 in FIG. 15), in some embodiments, the resulting line isused to extrapolate failure points at numbers of revolutions notactually tested. For example, in some embodiments, a number of testpoints may be determined, each having a low number of revolutions/cycles(e.g., 100-1000 revolutions), to generate the profile (line 1502) andthen extrapolate what the load failure will be at larger numbers ofrevolutions (e.g., at 10,000-100,000 revolutions) without actuallyhaving to determine these test points, saving time in generating theload vs. fatigue profile.

Additionally, still referring to FIG. 15, knowing the load vs. fatigueprofile of the shaft, a threshold may be defined in terms of the loadthat is sufficient to cause the shaft to fail during normal intended useof the shaft. By knowing where this load threshold crosses the load vs.fatigue profile (line 1502), it can be estimated the life of the shaftin its intended use. For example, in one embodiment of a shaft used in agolf club, it is assumed (for sake of example) that the load thresholdis 15 lbs. A horizontal threshold line 1504 then exists on the graph ofFIG. 15 at 15 lbs. This is the example load that would normally causethe shaft to fail with the use of the shaft within a golf club strikinga golf ball. Once the profile (line 1502) is determined or estimated,the point 1506 at which the load threshold 1504 crosses line 1502determines the life of the shaft. According to the graph of FIG. 15,this would occur at about 50,000-70,000 cycles (revolutions). That is,at below the number of cycles or revolutions of point 1506, the shaftwould not fail, but at or above the number of cycles or revolutions ofpoint 1506, the shaft will fail.

Referring next to FIG. 16, a variation of the plot of FIG. 15 is shownas a semi-log plot of moment in lbs-in vs. revolutions. Instead ofplotting load, a moment is calculated, such as at point P3 and plotted.This plot may be used for similar purposes as the plot of FIG. 15. It isnoted that the plot of FIG. 16 includes the plots of two different modelshafts (shaft #1 and #2) designed to have different flexcharacteristics. As can be seen, lines 1602 and 1604 illustrate themoment vs. fatigue profile for the two shafts, each having a differentR² value. In other embodiments, multiple different shafts of the samemodel may be tested to generate statistically more accurate profiles,for example, by averaging the failure points and moments for each shaft.For example, this would yield an average number of revolutions forfailure at a given test moment. These average values should providestatistically more accurate profiles.

The following description provides one specific example of the operationof an embodiment of a shaft testing device. It is understand that thisis provided for example, only and that other embodiments may operatedifferently. This example refers to the embodiment described in FIGS.6-11. In this example, the shaft testing device supports the followingmodes: power on; standby to save power, resume, pause/interruption;emergency stop; cancel, and power off. The shaft testing device of thisexample provides the following modes: (I) static bend mode; (II) fatiguetest mode; and (III) fatigue life mode which predicted life of shaftbefore failure.

In the static bend mode (mode I), the user inputs include: partdescription; shaft number; part type (Driver, Fairway, Hybrid, or Iron);operator name; date (mm/dd/yy); rotation speed (rpm) (zero if notrotating); interval displacement or load between rotation; load to reachbefore rotations at intervals will occur (kg or N); displacement Speed(mm/min); and failure definition (% of load drop). The sensor inputsinclude: doors open or closed (two doors); home and maximum displacementpositions; locations of upper and lower wheel supports; load cellreadings at the upper and lower wheel supports; and Emergency Stopcondition. The outputs include: shaft tip position from home (mm); loadfrom load cells (kg or N); calculated moment at shaft tip (kg*m or N*m);effective tip stiffness: slope of calculated load at tip divided bydisplacement (kg/m or N/m); max load (kg or N); max displacement (mm);max moment (kg*m or N*m); shaft radial orientation at failure (Deg);chart of applied calculated moment vs. displacement or applied load attip vs. displacement. The general sequence of events in this embodimentis as follows. First, the Static Bend Test is selected from the userinterface. The interface prompts the user to adjust the support wheelsto their proper location, load a shaft into the machine, and shut thedoors. Then, the user interface prompts for user inputs. If rotationspeed is nonzero, user must specify: rotation interval; and load ordisplacement to reach before rotations will occur. The user inputsloaded. The electrical components are powered on, light mode is set tobright and door sensors are checked. If any door is open: the interfaceprompts user to shut the doors; all machine movement is restricted untilthe door is closed.

When the doors are shut, the interface prompts the user if they'd liketo Resume or Cancel the test. Next tare (zero out) the load cells. Thelinear actuator then displaces the shaft. Establish the ‘0’ location(separate from Home position) when the Load cells see the first load. Ifno loading is seen while part is moving, stop after X movement andprompt user that no part is in fixture or there is an error. If rotationspeed is zero, continue displacement until failure criteria is met. Ifat any time the displacement stays in one location for Y time theninitiate the stop sequence and warn the user that the strength of theshaft exceeds the machine's capability. Nest, stop and maintaindisplacement at failure. Output data is required. If rotation speed isnonzero and the load is reached to begin rotations, rotate the part360°. When the rotation is complete, displace the part to the nextinterval displacement or load, stop, and rotate again. Repeat untilfailure criteria is met. Stop and maintain displacement at failure.Output required data. If the max displacement sensor is triggered beforethe failure criteria is met: Stop the displacement at the maxdisplacement location; User interface alerts user that max displacementhas been reached; and Output load at maximum displacement. The userinterface communicates test is complete and prompts user to save data.The user interface prompts user to bring the linear actuator back to theHome position (allows the user to investigate the break under loading,if desired). If Yes to above, linear actuator returns home (2 uniquespeeds to return home).

Regarding the fatigue test program mode (mode II), the user inputs areas follows: Part description; Shaft number; Part Type (Driver, Fairway,Hybrid, or Iron); Operator name; Date (mm/dd/yy); Rotation speed (rpm);Acceleration of rotation; Test load/moment; Test to failure includingdefining failure criteria; Test to cycle count including inputting maxcycles to test to; Displacement Speed High (mm/min); and DisplacementSpeed Low (mm/min). The sensor inputs are as follows: Doors open orclosed (two doors); Home and maximum displacement positions; Locationsof upper and lower wheel supports; Load cell readings at the upper andlower wheel supports; and Emergency Stop condition. The outputs are asfollows: Shaft tip position from home (mm); Measured Loads from loadcells (kg or N); Calculated moment at shaft tip (kg*m or N*m); Effectivetip stiffness: Slope of calculated load at tip divided by displacement(kg/m or N/m); Shaft Displacement (mm); Shaft radial orientation atfailure (Deg); Cycles; Test time (hours: min); Chart of appliedcalculated moment vs. displacement or applied load at tip vs. cycles.The general sequence of events in this embodiment is as follows. First,the fatigue test mode is selected from the user interface. The userinterface then prompts the user to adjust the support wheels to theirproper location, load a shaft into the machine, and shut the doors. Theuser interface then prompts for user inputs. If “test to failure” ischosen, the user must specify Failure criteria. If the “test to cycle”is chosen, the user must specify: Max cycles for test. Next, user inputsare loaded and all electrical components are powered on. The light modeis set to Bright. Next, door sensors check status of doors. If any dooris open: the interface prompts user to shut the doors; and all machinemovement is restricted until the door is closed. When the doors areshut, the interface prompts the user if they'd like to Resume or Cancelthe test. Next, Tare the load cells. Next, the linear actuator displacesshaft at high speed until Y load is reached (for speed efficiency).After Y load is reached, the linear actuator displaces the shaft at lowspeed (for loading accuracy). If no loading is seen while part ismoving, stop after X movement and prompt user that no part is in fixtureor there is an error. If at any point the either of the Load Cell loadsreaches 80% of capacity (in this case 80 lbs), stop the sequence andwarn the user. When the user input target is reached, the main motorspins the shaft one revolution slowly, taking load measurements at allcircumferential positions (all 360°). The PLC determines which angularposition associates with the max load and establishes that point as the0° location. The main motor then spins the shaft to the 0° location(this position directly facing the load cell). Next, accelerate theshaft to user input RPM requirement. If the maximum travel sensor isactivated, stop displacement and the user interface alerts user maximumtravel has been reached and test load must be lowered or test can beperformed at the max travel. Next output rates are defined. If thefailure criteria or cycle count is reached, stop rotations. The userinterface communicates the test is complete and prompts user to savedata. The user interface then prompts user to bring the linear actuatorback to the Home position (allows the user to investigate the breakunder loading, if desired). If Yes, then the linear actuator returnshome (2 unique speeds to return home).

The fatigue life test program mode (mode III) is an automated procedurethat guides the user through Mode I and Mode II to create a semi-logfatigue life chart. Referring to the flow chart 1700 of FIG. 17, Mode Iwill run in a loop until the operator chooses to exit the loop. Forexample, the user will load a part (shaft) for testing according to modeI (Step 1702), run mode I (Step 1704) and decide whether to repeat thetest (Step 1706). Mode II will run at specifically calculated loadingconditions, L_(Y), where Y is the number of loading conditions andranges from 3 to 10 (with 4 as a default value). When one loadingcondition test is completed (i.e., the answer to decision Step 1708 isno, the system will move to the next loading condition (Step 1710) andso forth until all loading conditions are completed (this is called theL_(Y) Loop). Within each loading condition test (i.e., within each valueof Y) is a loop that repeats Mode II for the same loading condition(this is called the Mode II Loop). For example, the user will load apart (shaft) for testing according to mode II (Step 1712), run mode II(Step 1714) and decide whether to repeat the test (Step 1716) whilemaintaining the same loading condition (Step 1718). Therefore, eachloading condition tested contains one or more tests at that specificloading condition.

For mode III, all inputs and outputs are the same as described in ModesI and II. However, since Mode III is a combination of both Modes I andII, the user will need to enter all required inputs for both Modes I andII prior to initiating the test. As Mode III runs through its programsequence, inputs provided prior to initiating the test are not requiredto be re-entered. Again, the flowchart of FIG. 17 provides a generalflow of Mode III.

A more specific sequence for the Mode I loop of the flowchart of FIG. 17according to one embodiment is as follows. (a) The user interfacerequests required inputs for both Mode I and Mode II operations. Then,(b) the user interface communicates to the user that a Static Break Testwill initiate and prompts the user to load the shaft into the shafttesting device. (c) Mode I will execute as described above. (d) Afterthe mode I test is complete, the user interface: displays the testresults; asks if the user accepts the results or would like to deletethe test; and prompts the user if they'd like to run another test toobtain averages and statistical values. If the user chooses to acceptthe single test data and move on, exit the Mode I loop and go to theMode II loop. If the user chooses to repeat another test, repeat (b)through (c) above. (e) Whenever more than one test is complete, the userinterface: Displays the test history within the Mode I loop; Displaysthe test results from the latest test; Displays the statisticalinformation from the total number of tests; Asks if the user accepts theresults or would like to delete any of the tests; and Prompts the userif they'd like to run another test to obtain better averages andstatistical values. If the user chooses to accept the statistical dataand move on, exit the Mode I loop and go to the Mode II loop. If theuser chooses to repeat another test, repeat (b), (c), and (e) above.

A more specific sequence for the Mode II loop of the flowchart of FIG.17 according to one embodiment is as follows. (a) Mode II uses theStatic Break data to automatically set up the Mode II tests at differentloading conditions. (b) The user interface allows the user to choose howmany different loading conditions, Y, they want to run (between 3 and10, default value at 4). (c) The user interface communicates to the userthat a Fatigue Test will initiate at load L_(Y) and prompts the user toload the shaft into the shaft testing device. (d) Mode II will executeas described in the Mode II section. (e) After the test is complete, theuser interface: Displays the test results; Asks if the user accepts theresults or would like to delete the test; and Prompts the user if they'dlike to run another test to obtain averages and statistical values. Ifthe user chooses to accept the single test data and move on, exit ModeII and go to the L_(Y) Loop. If the user chooses to repeat another test,repeat (c) (d) above at the same loading condition, L_(Y) (Mode IILoop). (f) Whenever more than one test is complete, the user interface:Displays the test history within the Mode II loop; Displays the testresults from the latest test; Displays the statistical information fromthe total number of tests in the L_(Y) loop; Asks if the user acceptsthe results or would like to delete any of the tests; and Prompts theuser if they'd like to run another test to obtain better averages andstatistical values. If the user chooses to accept the single test dataand move on, exit Mode II and go to the L_(Y) Loop. If the user choosesto repeat another test, repeat (c) (d) above at the same loadingcondition, L_(Y) (Mode II Loop).

The L_(y) Loop of FIG. 17 repeats the same functions as the Mode II loopbut increments the different loading conditions, Y, until the last Y iscompleted. Data from the Static Break Test and Fatigue Life Tests arecharted in a semi-log plot continuously as the data is gathered forimmediate, real-time review by the operator. The chart should serve as aguide to the operator whether to repeat, delete, or accept tests.

Turning now to several additional embodiments, shaft testing devices areprovided that test for torsional fatigue of the shaft. One factor in theoverall strength of a shaft is its torsional fatigue strength. Torsionalfatigue strength of a shaft is relevant in the golf industry because agolf shaft, when in use, has a torque repeatedly applied to it. Thus,for this and other reasons, there is a need to be able to simply andaccurately determine the torsional fatigue strength of a shaft.

In some embodiments, a device for evaluating the torsional fatigue of ashaft is provided comprising a frame; a first holder coupled to theframe, the first holder adapted to hold a first portion of a shaft; asecond holder coupled to the frame, the second holder adapted to hold asecond portion of the shaft; and wherein the second holder is adapted tointroduce an angular displacement of the second portion of the shaftrelative to the first portion of the shaft.

Some embodiments provide a method for testing torsional fatigue of ashaft comprising holding a first portion of a shaft; holding a secondportion of the shaft; and angularly displacing the second portion of theshaft relative to the first portion.

In some embodiments, a torsional testing machine and related methods areprovided to test the strength of a shaft under the strain ofbidirectional oscillating angular displacement, similar to the force ona golf shaft when in use. Angular displacement refers to an amount ofrotation of an object about an axis and may also be referred to asrotational displacement. In some embodiments, at least two portions(e.g., two ends) of the shaft are held while one portion is angularlydisplaced relative to the other portion in order to determine atorsional breaking point of the shaft. In some embodiments, a firstportion and a second portion of the shaft are held while an angulardisplacement is applied to the second portion in order to generate aprofile of the torsional fatigue life of the shaft. Generally, in someembodiments, when testing the torsional fatigue life of a shaft, atleast two portions (e.g., ends) of the shaft are maintained in fixedpositions while one of the portions is rotated in an oscillating mannerwhile measuring load forces exerted by the shaft at one or more pointsof the shaft. Over time, a profile can be generated of the torsionalfatigue life of the shaft, for example, the ability of the shaft towithstand torque at a given acceleration and/or a given angulardisplacement over time. In some embodiments, the testers and methodsprovided are safe and quiet to use, can be performed quickly, and can beused in an automated fashion without human supervision.

Referring next to FIG. 18, a free body diagram of a torsional fatiguedevice 1800 is shown in accordance with some embodiments of the presentinvention. FIG. 18 depicts a shaft 102 having a butt end and a tip end,the butt end held by a clamp 1802, the shaft tip end held by a chuck1804, the chuck being rotatable and coupled to a motor 1806, the motoradapted to apply a rotational force to the chuck. A controller 1808 orhuman-machine interface (HMI) is coupled to the motor. A load cell (notshown) is also coupled to the motor.

In operation, the shaft butt end is loaded into a clamp 1802. In someembodiments, the shaft butt end is loaded into a lathe chuck, block orother device to fixedly hold a shaft. The clamp is tightened so as tohold the shaft butt end in a fixed position. In some embodiments, theclamp is manually tightened. In some embodiments, the clamp isautomatically tightened. In some embodiments, during operation, theshaft butt end that is fixedly held does not rotate within the clamp ormove in any of the X, Y or Z-directions.

The shaft tip end is loaded into a chuck 1806 and locked in place. Insome embodiments, the shaft tip end is loaded into a clamp, block orother device to fixedly hold a shaft. The chuck is tightened so as tohold the shaft tip end in a fixed position. In some embodiments, thechuck is manually tightened. In some embodiments, the chuck 1804 isautomatically tightened. In some embodiments, during operation, theshaft tip end that is fixedly held does not rotate within the clamp ormove in any of the X, Y or Z-directions. In some embodiments, the chuckfits about the shaft tip end about to the same extent that a hosel of agolf club head covers a golf shaft.

It is noted that the clamp 1802 and the chuck 1804 that hold the shaftbutt end and shaft tip end, respectively, may be generically referred toas a holder or support that holds or supports a portion (e.g., the shaftbutt end, or shaft tip end) of the shaft. In some embodiments, the chuckof is bi-directionally rotatable. That is, the chuck is adapted torotate both clockwise and counterclockwise. When the shaft tip end islocked, or otherwise fixedly held in the chuck, rotation of the chuckintroduces a rotational or an angular displacement of the shaft tip endrelative to the shaft butt end.

Still referring to FIG. 18, a motor 1806 (e.g., a rotary motor) is shownthat is adapted to introduce a rotational force on the chuck. Inoperation, the motor rotates the chuck which, in turn, introduces anangular displacement on the shaft tip end that is fixedly held in thechuck. The motor controls partial rotations of the chuck. The motor alsohas the capability to be easily manipulated or programmed for automaticoperation using a controller/HMI and can run for extended periods oftime under nominal loads. In some embodiments, the motor includes arotary encoder in order to determine (and output) its circumferentiallocation at all points in time.

In some embodiments, the torsional fatigue machine includes one or moreload cells. In some embodiments, the load cell is coupled to the motorand measures the stress on the shaft due to the angular displacement ofa first portion of the shaft relative to a second portion of the shaft.In some embodiments, the load cell is coupled to the shaft 102. Anamplifier (not shown, but similar to amplifier 220) is used to increasethe signal output by the load cell. The load applied to a shaft, andmeasured by the load cell, is dependent upon many factors including thethickness and strength of the shaft, the amount of angular displacementand the acceleration at which the angular displacement occurs.

In some embodiments, a frame (not shown) supports the various featuresof the torsional fatigue machine. In some embodiments, the frame is madeof aluminum for its structural members. It is understood that the framemay comprise one or more frames or one or more frame members or otherstructure to support the various components herein described. In someembodiments, the frame is generally rectangular. The height of the framemay be adjusted to accommodate shafts of various sizes. In someembodiments, the frame supports the chuck, clamp and motor.

When a shaft is secured at both ends and the machine is in operation,the motor 1806 rotates the chuck 1804 causing an angular displacement inthe shaft tip end relative to the shaft butt end. In some embodiments,the amount of angular displacement introduced by the motor is determinedat least in part using a measured amount of angular displacement of agolf shaft as measured during a golf swing. In this manner, the fatiguetester machine mimics the force applied and/or moment generated at agolf shaft when it is in use. According to some embodiments and usingdata gathered from measurements and/or input by the user, an angulardisplacement is determined that enables the torsional fatigue strengthof the shaft to be tested. The motor 1806 rotates the chuck from anequilibrium position to a first angular displacement with anacceleration profile. The motor then returns to the equilibrium positionfrom the first angular displacement and proceeds in the direction ofangular momentum, i.e., in the opposite direction of the first angulardisplacement, to a second angular displacement at the same accelerationprofile. In several embodiments, the first and second positions ofangular displacement are of the same magnitude, but are on oppositesides the equilibrium position. The motor continues to rotate the chuck,and thus the shaft tip end, from the first to the second angulardisplacements, and vice versa, through the equilibrium. In preferredembodiments, the motor does not rotate the chuck 360 degrees. In thismanner, according to several embodiments, the chuck, by virtue of themotor, introduces a bidirectional oscillating angular displacement tothe shaft.

The acceleration profile or the acceleration of the motor's oscillationsare input into the controller/HMI. Similar parameters as those describedherein, such as with reference to FIGS. 12 and 13 may be used. In thismanner, the fatigue tester machine mimics the force applied to a golfshaft or the moment generated by a golf shaft when it is in use sincethe acceleration profile of a shaft under test is similar to theacceleration of angular displacement experienced by a golf shaft when inuse. The torsional fatigue strength of the shaft can be determined usingdata gathered from measurements of a shaft that is oscillating with anacceleration profile in accordance with this description.

In some embodiments, a user initiates testing by interacting with ahuman machine interface (HMI) or other computer. In some embodiments, auser initiates testing by interacting with a PC coupled to the system(i.e., a controller/HMI includes a personal computer). In someembodiments, the system runs until manually terminated. In alternativeembodiments, the system is automatically terminated when failure occurs(a shaft breaks) or a stopping event occurs. A stopping event is, forexample, an elapse of a user-selected amount of time, a change in load,or other event in response to which the testing will terminate.

While the machine is running, the load measurements and correspondingrotary location measurements or readings are output to a controller tobe stored and/or processed (or further output to a computer). Load cellmeasurements are correlated to circumferential positions measured by theencoder in order to output, display, and/or process load measurements.In some embodiments, the user can program the frequency at which torecord and/or display load measurements.

The torsional fatigue testers described herein may be used with avariety of different shafts, such as sports implements (e.g., golfshafts, pole vault shafts, baseball bats, etc.) or any other shaft thatis intended to experience torsional fatigue. Over a period of testing,torsional fatigue characteristics can be generated from loadmeasurements to determine the torsional endurance of a shaft, forexample, for quality control purposes.

In some embodiments, data from a load cell is sent to a PC (not shown)and a representation of the data displayed. Data relating to the load atone or more points on the shaft is sent to the PC. Data relating to thenumber of oscillations of the shaft is sent to the PC. In someembodiments, fatigue life of a shaft may be predicted based upon datagathered at the PC.

This specification describes several shaft testing devices and relatedmethods. In one embodiment, a shaft test comprises a frame, a firstshaft support coupled to the frame, the first shaft support adapted tosupport a first portion of a shaft at a first fixed position, and asecond shaft support coupled to the frame, the second shaft supportadapted to support a second portion of the shaft. The second shaftsupport is adapted to introduce a displacement of the second portion ofthe shaft relative to the first portion of the shaft. In one variation,the second shaft support holder is adapted to laterally move the secondportion of the shaft relative to the first portion to introduce alateral displacement to the shaft. In another variation, the shafttester further comprises a third shaft support coupled to a thirdportion of the shaft, the third portion in between the first portion andthe second portion, the third support adapted to support the thirdportion at a second fixed position such that the shaft bends about thethird portion when the second shaft support laterally moves the secondportion of the shaft relative to the first portion. In anothervariation, the shaft tester further comprises a linear bearing guidecoupling the second shaft support to the frame and adapted such that thesecond shaft support can be fixed at a plurality of locations along thelinear bearing guide. Additionally, the shaft tester comprises a motorcoupled to the shaft and adapted to rotate the shaft while laterallydisplaced. In a further variation, the first shaft support is adapted toallow the shaft to rotate when the shaft is experiencing the lateraldisplacement. In another variation, the first shaft support and thesecond shaft support are adapted to allow the shaft to rotate 360degrees when the shaft is experiencing the lateral displacement. Inanother variation, the shaft tester further comprises an encoder adaptedto measure an angular position of the shaft. In a further variation, thesecond shaft support fits about the second portion of the shaft about tothe same extent that a hosel of a golf club head covers a golf shaft. Iyet another variation, a load cell is coupled to the second shaftsupport for measuring a force due to the displacement of the shaft.

In another embodiment, a method for testing a shaft comprises the steps:holding a first portion of a shaft; holding a second portion of theshaft; and displacing the second portion of the shaft relative to thefirst portion. In a variation, the displacing step comprises laterallydisplacing the second portion of the shaft relative to the firstportion. In a further variation, the displacing step comprisesdisplacing the second portion of the shaft relative to the first portionand about a first support at a third portion of the shaft, the thirdportion in between the first portion and the second portion, the firstsupport adapted to maintain a fixed position such that the shaft bendsabout the third portion. In another variation, the method also comprisesrotating the shaft while maintaining the displacement. In anothervariation, the method also measures a load exerted by the second portionwhile displacing and rotating the shaft. In a further variation, themethod includes generating a profile of the load over time whiledisplacing and rotating the shaft. In another variation, the methodfurther measures a load exerted by the second portion while displacingthe shaft. And in another variation, the method generates a profile ofthe load over time while displacing the shaft.

In a further embodiment, a shaft tester comprises a frame, a firstholder coupled to the frame, the first holder adapted to hold a firstportion of a shaft and a second holder coupled to the frame, the secondholder adapted to hold a second portion of the shaft. The second holderis adapted to introduce an angular displacement of the second portion ofthe shaft relative to the first portion of the shaft. In one variation,the angular displacement is introduced by a motor coupled to the secondholder. In another variation, the tester includes an encoder coupled tothe motor and adapted to measure the angular displacement of the shaft.In a further variation, the tester includes a load cell coupled to themotor and adapted to measure a force due to the angular displacement ofthe shaft. In another variation, the second holder is a rotatable chuck.In a further variation, the second holder fits about the second portionof the shaft about to the same extent that a hosel of a golf club headcovers a golf shaft. In another variation, the second holder is adaptedto allow a bidirectional oscillating angular displacement of the secondportion of the shaft relative to the first portion of the shaft.

In a further embodiment, a method for testing a shaft comprising thesteps: holding a first portion of a shaft; holding a second portion ofthe shaft; and angularly displacing the second portion of the shaftrelative to the first portion. In one variation, the step of angularlydisplacing is accomplished at least in part by a motor. In anothervariation, the method measures with an encoder the angular displacementof the shaft. In another variation, the method measures with a load cella force due to the angular displacement of the shaft. In a furthervariation, the step of holding a second portion of the shaft isaccomplished at least in part by a rotatable chuck. In anothervariation, the step of holding a second portion of the shaft comprisesfitting a holder about the second portion of the shaft about to the sameextent that a hosel of a golf club head covers a golf shaft. And inanother variation, the step of angularly displacing comprises allowing abidirectional oscillating angular displacement of the second portion ofthe shaft relative to the first portion of the shaft.

While the invention herein disclosed has been described by means ofspecific embodiments, examples and applications thereof, numerousmodifications and variations could be made thereto by those skilled inthe art.

1. A shaft tester comprising: a frame; a first shaft support coupled tothe frame, the first shaft support adapted to support a first portion ofa shaft at a first fixed position; a second shaft support coupled to theframe, the second shaft support adapted to support a second portion ofthe shaft at a second fixed position; a third shaft support coupled tothe frame, the third shaft support adapted to support a third portion ofthe shaft at a third fixed position; an actuator coupled to the thirdshaft support and adapted to displace the third portion relative to thefirst portion and the second portion to cause a deflection in the shaft;a sensor coupled to one of the first support, the second support and thethird support and adapted to output a signal corresponding to a loadforce exerted by the shaft due to the deflection; and a controllercoupled to the actuator and adapted to control displacement of theshaft.
 2. The shaft tester of claim 1 further comprising a motor adaptedto rotate the shaft when the shaft experiences the deflection.
 3. Theshaft tester of claim 2 wherein the controller is adapted to control oneor more of a speed of rotation of the shaft, a time duration of therotation, an acceleration of the rotation, and a number of cycles of therotation.
 4. The shaft tester of claim 2 wherein the first shaftsupport, the second shaft support and the third shaft support areadapted to allow the shaft to rotate 360 degrees when the shaftexperiences the deflection.
 5. The shaft tester of claim 1 wherein thecontroller is adapted to control one or more of an amount of thedeflection, a force caused by the deflection, and a time duration of thedeflection.
 6. The shaft tester of claim 1 wherein the first portion isproximate a butt end of the shaft, the third portion is at a tip end,and the second is in between the first portion and second portion. 7.The shaft tester of claim 6 wherein the third shaft support fits aboutthe tip end of the shaft about to a same extent that a hosel of a golfclub head covers a golf shaft.
 8. The shaft tester of claim 1 whereinthe sensor comprises a load cell.
 9. The shaft tester of claim 1 whereinthe actuator adapted to laterally displace the third portion relative tothe first portion and the second portion to cause a lateral deflectionin the shaft.
 10. The shaft tester of claim 1 further comprising acomputer coupled to the controller.
 11. A shaft tester comprising: aframe; a first shaft support coupled to the frame, the first shaftsupport adapted to support a first portion of a shaft at a first fixedposition; a second shaft support coupled to the frame, the second shaftsupport adapted to support a second portion of the shaft at a secondfixed position; an actuator coupled to the second shaft support andadapted to displace the second portion relative to the first portion tocause a lateral deflection in the shaft; a sensor coupled to one of thefirst shaft support and the second shaft support and adapted to output asignal corresponding to a load force exerted by the shaft due to thelateral deflection; a motor adapted to rotate the shaft when the shaftexperiences the lateral deflection; and a controller coupled to theactuator and the motor and adapted to control the deflection androtation.
 12. The shaft tester of claim 11 wherein the controller isadapted to control one or more of an amount of a speed of the rotationof the shaft, a time duration of the rotation, an acceleration of therotation, and a number of cycles of the rotation.
 13. The shaft testerof claim 11 wherein the first shaft support and the second shaft supportare adapted to allow the shaft to rotate 360 degrees when the shaft isexperiencing the lateral deflection.
 14. A method for use in testing ashaft comprising: supporting a first portion of a shaft at a first fixedposition; supporting a second portion of a shaft at a second fixedposition; supporting a third portion of a shaft at a third fixedposition; displacing the third portion relative to the first portion andthe second portion causing a deflection in the shaft; outputting asignal corresponding to a load force exerted by the shaft due to thedisplacing; and controlling a displacement of the shaft.
 15. The methodof claim 14 further comprising rotating the shaft when the shaftexperiences the deflection.
 16. The method of claim 15 wherein thecontrolling step comprises controlling one or more of a speed ofrotation of the shaft, a time duration of the rotation, an accelerationof the rotation, and a number of cycles of the rotation.
 17. The methodof claim 15 further comprising allowing the shaft to rotate 360 degreesduring the rotating step and while the shaft experiences the deflection.18. The method of claim 15 wherein the rotating comprising rotating theshaft when the shaft experiences the deflection until the shaft fails.19. The method of claim 14 wherein the controlling step comprisescontrolling one or more of an amount of the deflection, a force causedby the deflection, and a time duration of the deflection.
 20. The methodof claim 14 wherein the first portion is proximate a butt end of theshaft, the third portion is at a tip end, and the second is in betweenthe first portion and second portion.
 21. The method of claim 20 whereinthe third portion is supported about to a same extent that a hosel of agolf club head covers and supports a golf shaft.
 22. The method of claim14 wherein the displacing step comprises laterally displacing the thirdportion relative to the first portion and the second portion causing alateral deflection in the shaft.
 23. The method of claim 14 furthercomprising measuring the load force.
 24. A method for use in testing ashaft comprising: supporting a first portion of a shaft at a first fixedposition; supporting a second portion of a shaft at a second fixedposition; laterally displacing the second portion relative to the firstportion and the second portion causing a lateral deflection in theshaft; outputting a signal corresponding to a load force exerted by theshaft due to the displacing; rotating the shaft during the displacingstep; and controlling the displacing and the rotating of the shaft. 25.The method of claim 24 wherein the controlling step comprisescontrolling one or more of an amount of a speed of the rotation of theshaft, a time duration of the rotation, an acceleration of the rotation,and a number of cycles of the rotation.
 26. The method of claim 24wherein the rotating step comprises rotating the shaft over 360 degrees.